A plasma TV is a high definition (HDTV) alternative to the standard cathode ray televisions sold today. A plasma TV provides sharp images and vibrant colors, especially when used in conjunction with high definition broadcasts. Quite often a plasma TV is designed in a 16:9 ratio for wide screen movie formats, as opposed to the box-like 4:3 ratio of standard televisions. A quality plasma TV is not cheap, however. Units start at $2,000 USD and can be as high as $15,000 USD or more.
One of the chief selling points of a plasma TV is a flat screen, which allows it to be mounted directly on a wall without a lot of clearance required. Investors in a plasma TV may also employ surround-sound theater speakers and high-end receivers to complete the feeling of luxury. Plasma televisions have become status symbols among technophiles and other wealthy consumers.
The science behind a plasma TV is very complicated. 'Plasma' is a scientific term referring to gases like neon and xenon which glow when exposed to an electrical field. Plasma is sometimes called the fourth state of matter, after liquids, solids and gases. Think of a neon sign or fluorescent light bulb to understand plasma as it applies here.
In a plasma TV, the individual pixels are made from three tiny containers of an inert gas such as neon or xenon. There are literally hundreds of thousands of these tiny tubes on an average plasma TV screen. All of these individual pixels are sandwiched between two electrically-charged plates. Remember that plasma glows when exposed to an electrical current. A computer processing unit receives signals from a cable or broadcast antenna which tells it how to reassemble the entire picture hundreds of times per second.
The computer controls the electrical field down to individual pixels, allowing different combinations of colors to glow. The viewer is usually not aware of all the changes, because his or her brain is processing all of the information as a continuously moving image. Because a plasma TV screen contains quite a few more pixels than a standard television, the image is noticeably sharper. Each pixel combination can reproduce an exact hue, not a quick approximation. This means the colors are usually deeper and richer.
The main drawback of a plasma TV system is vulnerability to damage. If a hard object strikes the screen, hundreds of individual gas-filled tubes instantly lose their ability to glow. Replacing all of those elements is a time-consuming and expensive process, if it can be done at all. Owners of plasma TV systems should always consider purchasing insurance and extended warranties, since the most common fix appears to be total replacement of the screen. Because the gas forming the plasma can leak or become less reactive to electrical charges, plasma TV systems do have a limited shelf life. It may take several years before a noticeable change in picture quality, but the cumulative effects are similar to what happens in neon and fluorescent lighting-eventually the gas inside the tube will begin to flicker instead of burning steadily.
How it Works ?
Traditional" televisions use cathode ray tubes, in which a gun fires a beam of electrons inside a large glass tube at phosphor atoms at the other end. The electrons excite the phosphor atoms, causing them to light up as pixels. The image is produces by lighting up different areas of the phosphor coating with different colors (red, green, blue) at varying intensities. While this sort of TV produces nice images, physically they are bulky. In order to increase screen size, you have to increase the length of the cathode ray tube. So, a big-screen TV of this sort will take up a lot of room.
Flat panel plama TVs on the other hand, can have large screens and only be a few inches thick. The basic idea of a plasma display is to use tiny fluorescent lights--made up of either red, blue, or green-- to form an image on the screen. Plasma refers to gas made up of free-flowing ions and electrons. When you introduce many free electrons into the gas by exerting electrical current across it, they collide with the gas' atoms knocking loose other electrons. This forms ions (an atom with a net positive charge).
In a plasma with an electrical current running through it, negatively charged particles are rushing toward the positively charged area of the plasma, and positively charged particles are rushing toward the negatively charged area. While the particles are bumping into each other, these collisions excite the gas atoms (xenon and neon) in the plasma causing them to release photons of light. Most of light released is UV light, which is invisible to the human eye. BUT this UV light can be used to produce light in the visible spectrum.
The xenon and neon gas is contained in hundreds of thousands of tiny cells positioned between two glass plates. Electrodes are positioned between the glass plates; the transparent display electrodes, which are surrounded by an insulating dieletric material and covered by magnesium oxide, are mounted above the cell. So essentially, to ionize the gas in a particular cell, the plasma display's computer charges the electrodes that intersect at that cell---it does this thousands of times in a fraction of a second. This induces the gas to release UV photons which intersect with the phosphor material which coats the inner part of the cell. This cause it to release a photon of visible light.
Every pixel in a plama display is made up of three seperate sub-pixels----red, blue, and green---which can be activated alone or together to create a picture. And, by varying the pulses of electricity through the different cells, the intensity of each subpixel can increase or decrease. This results in a very bright picture that looks good from any angle, but surprisingly, the image quality is not as good as the highest quality cathode ray tube televisions.
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Chandra Bhushan on 2009-03-03 23:36:27 wrote,
Plasma Plasma Plasma... I hav been hearing this word a lot from a long time but never got the correct meaning of plasma.. But this article has clear all my concept about Plasma